The last section on firewalls focuses on the concept of stateful inspection. Stateful inspection
is also referred to as stateful packet filtering. Most of the devices used in networks don’t keep
track of how information is routed or used. Once a packet is passed, the packet and path are
forgotten. In stateful inspection (or stateful packet filtering), records are kept using a state table
that tracks every communications channel. Stateful inspections occur at all levels of the network
and provide additional security, especially in connectionless protocols such as User Datagram
Protocol (UDP) and Internet Control Message Protocol (ICMP). This process adds complexity
to the process. Denial of service (DoS) attacks present a challenge because flooding techniques
are used to overload the state table and effectively cause the firewall to shut down or reboot